I think the full shopping list is-
-Maybe a switch so you can easily turn off the LED's to save battery life
-wire to go between battery pack and LED strip (with a switch in the middle, if desired)
-electrical tape or heat shrink tubing to cover wire splices
-whatever items you need to attach the pack, LED's, switch, and wiring to your costume.
I took tons of photos at NYCC2012! See Saturday here,
Sunday B&W Film here,
and a couple Sunday digital shots here.